The mitral valves are two pieces of valves attached to the periphery of the left atrioventricular orifice (as shown in FIG. 1), connecting to the papillary muscles through the chordaetendineae, and functioning to prevent the blood in the left ventricle from flowing back to the left atrium.
Mitral valve regurgitation (MR) is caused by organic or functional lesion of the mitral valve leaflets and associated structures, leading to it insufficient coaptation of the anterior and posterior leaflets of the mitral valve. As a result, the blood flows back from the left ventricle to the left atrium, causing a series of pathological and physiological changes. Serious MR will lead to left ventricle enlargement, impair the systolic function of the left heart, and finally cause a heart failure. Meanwhile, the pressure of the left atrium also increases due to the regurgitation, easily causing the enlargement of the left atrium, atrial fibrillation, and pulmonary artery hypertension. The prognosis of the MR is poor. The annular mortality rate of patients who have the symptoms but do not undergo surgery is about 5%. Moreover, the five years mortality rate of patients complicated with serious heart failure is up to 60%. Meanwhile, the MR is also one of the most common heart diseases. According to the statistics, the prevalence rate of MR among the people who are over 65 and over 75 years old are 6.4% and 9.3% respectively. With the development of the economy and the society and the aging of the population, this rate shows a significantly rising trend.
Clinical trials show that the drug therapy can only relieve the symptom of the patients, without extending the survival period of the patients or providing operation time. Surgical valve repair or replacement operations are deemed as the standard treatment of the disease, and has been proven to be effective to relieve the symptom and prolong the life of the patients. However, the operation has the deficiencies such as serious trauma, heavy postoperative pain, slow recovery, high risk, and so on. Furthermore, patients with advanced age, thoracotomy history, poor cardiac function, or along with multiple organ dysfuntions, are usually refused to be operated on due to the high risk of the operation. Thus, developing a minimally invasive and low risk treatment device to treat the MR has the significant social benefit and can meet the market demand. Recently, with the break-through development of the interventional treatment technology for heart valves, the MR interventional device has currently become one of the focused directions of the research on the cardiovascular device, both domestically and overseas.
The valve clamp or clamp devices developed based on the technical principle of the surgical edge-to-edge suture of the valve is currently most recognized due to high safety, simple technical principle, and high feasibility. The technical principle of the surgical edge-to-edge suture of the valve is shown in FIGS. 2a and 2b. When the mitral valve regurgitation occurs, during the cardiac systolic period, edges of the two leaflets of the valve cannot close sufficiently, leaving a gap between them. As a result, the blood in the left ventricle flows back from the gap to the left atrium. Surgical edge-to-edge suture technique is to suture the intermediate points on the edges of the two leaflets of the mitral valve. Thus, during the cardiac systolic period, the gap between the leaflets of the valve is changed from one big hole into two small holes, so as to reduce the mitral valve regurgitation (FIG. 2a). Moreover, during the cardiac diastolic period, the blood flowing into the left ventricle, while the opening of mitral valve is not affected (FIG. 2b). The only minimally invasive interventional device for treating MR, which is approved and available on the market internationally, is MitraClip manufactured by Evalve corporation, and is a valve clamping device. However, MitraClip has a complex operating system, and high manufacturing cost. During the procedure, the device needs to go through the vein, the right atrium, the atrial septum, the left atrium, and finally reach the left ventricle. The access path is long with many turning points. Thus, the procedure is complex. The operators need to repeatedly and finely adjust the bends, the direction, the horizontal position, and the vertical depth of the delivery system until an ideal location is reached to clip the valve. Thus, the operators usually need to spend a lot of time to finish an operation, which is a drawback resulting in a lot of criticism.
Currently, in China, there is no MR device available in the market or under clinical trials. Thus, developing the interventional device for MR has the significance. Even though the Chinese patent application number CN102860846A discloses an edge-to-edge clamping device, the device is used for the tricuspid valve regurgitation, and cannot be used to treat the mitral valve regurgitation. Additionally, when the device is clipping the leaflets of the valve, the leaflets of the valve are not further clipped to close toward the central line, leaving a gap between the leaflets. Thus, the blood can flow through the gap. Accordingly, the efficacy of the operation is reduced greatly.
Thus, persons of ordinary skill in the art are making efforts to develop an interventional device for MR with a low cost, easy operation, and ideal effect.